The present invention relates to the clarification of liquids and more particularly to a novel method and apparatus for effecting clarification of liquids having particulate material entrained therewithin. The apparatus utilizes a novel means for continuously and effectively cleaning a filter employed to retain the particulate material.
In many industrial, food processing, agricultural and forest products applications, it is often necessary to clarify various liquids which have become entrained with particulate material. Typical examples include hot water block heating systems, log yard run-off, stack scrubbers, reclamation of river or irrigation ditch water and filtration of glue spreaders or dryer wash downs. In all of the above processes, some type of filter mechanism or catchment apparatus is provided for removing the particulate matter from a liquid stream so that the liquid may be reclaimed for subsequent reuse. However, in all of the above processes, a significant problem remains in the continuous requirement for liquid reclamation, and also in the concomitant requirement of periodic cleaning of the mechanism or filter which retains the particulate material. Cleaning is necessary to prevent the undesireable accumulation of particulate material not only on the surface of the filter, but also to remove that material which has become lodged in the filter's interstices.
Problems attending the clarification of water in the forest products industry may be illustrated by the following example in reference to what is referred to as a "hot water block heating process". Such a process is used to soften the fibers in logs or "blocks", which have been substantially debarked, prior to the blocks being peeled into veneer by a veneer lathe. It is necessary to soften the fibers to enhance peeling, and to this end, the blocks are loaded initially into steam vats where steam in the form of hot rain saturates the logs. The water, as it falls over and saturates the blocks, becomes contaminated with foreign matter or particulate material such as bark remnants, dirt, sand, etc. In order to reclaim the water, it is necessary to direct the contaminated water to a sediment tank where the large particles float to the surface. The remainder liquid, which still includes particulate matter, is then directed to a filtering device such as a filter screen. The filter screen can become clogged and substantially inoperable after a period of time, necessitating time consuming and burdensome cleaning.
Previous attempts have been made to provide a means for cleaning filter screens, but generally involve some type of vibrating or rotating mechanisms which impart motion to the filter screen itself. Such mechanisms generally are complex, expensive and subject to mechanical inefficiencies and breakdowns.
Accordingly, it is a general object of the present invention to provide a method and apparatus for effectively and continuously cleaning a filter means, such as a filter screen, in a water reclamation process, so that the filter means does not become clogged or impacted with particulate material. To this end, the present invention contemplates a novel filter-cleaning means in which a fluid flow, preferably in the form of a spray, is continuously directed against a filter means and the particulate material retained thereon, to effect relative movement between the particulate material and the filter means thereby to "sweep" the particulate material away.
It is another object of the present invention to provide a method and apparatus in which the fluid flow directed against the particulate material originates from a dispensing means selectively shiftable relative to the filter means. The dispensing means is mounted on a carriage means which is operable for selective, reciprocal shifting relative to the filter means. By directing the fluid flow against the filter means at variable locations thereon, the entire filter area, or a substantial portion thereof, is cleaned.
It is another object of the present invention to provide a dispensing means, as described above, incorporating upper and lower nozzle means mounted on the carriage means. The upper nozzle means are disposed for directing fluid flow against the upper surface of the filter means with the lower nozzle means, also mounted on the carriage means, being mounted beneath the filter means for directing fluid flow upwardly against the bottom surface of the filter means.
The net effect of the construction as described above is to "sweep" particulate material on top of the filter means downstream therefrom while the lower nozzle means, oriented to direct fluid flow substantially vertically upwardly, dislodges particulate material which may have become lodged or impacted within the interstices of the filter means. By continuously reciprocally shifting the dispensing means, particulate matter is continuously swept away and dislodged from the filter means.
Still another object of the present invention is to orient the nozzle means in a predetermined manner relative to the filter means. Elaborating further, the filter means is slightly tilted downwardly in the downstream direction, and the upper nozzle means are directed at an angle or obliquely relative to the filter means so that as particle-laden liquid is discharged onto the filter means, it tends to flow downwardly toward a discharge end with the particulate material, retained on the filter means, also being moved downstream due to the reciprocal impingement action of the upper and lower nozzle means.
These and additional objects and advantages of the present invention will be more particularly understood after a consideration of the drawings and the following detailed description of the preferred embodiment.